Screen for picture projection



July 10, 1928. 1,676,553

E; R. HEWITT SCREEN FOR PICTURE PROJECTION Filed March 13, 1925 l NVE. TOR EC/wora/ E/Zww 44B ATTORNEY Patented July 10, 1928.

UNITED STATES EDWARD R. HEWITT, OF MIDVALE, NEW JERSEY.

SCREEN FOR PICTURE PROJECTION.

Application filedMarch 13, 1925. Serial No. 15,363.

This invention relates to screens, as for state with the crystals themselves opaque example those on which moving pictures are projected or on which stereopt con pictures or any picture or projecting device by light for which the-best visibility is desired for those observing the screen. In particular the screens involving this invention provide a very material improvement over the screens heretofore used-for moving pictures, as this invention provides for assuring a greater amount of light being reflected from the screen, visibility at a much greater lateral angle, that is divergent from a line normal to the screen or the line of projection onto the screen, production on such screen or screen surfaces at low cost, with durability and various other advantages which will appear from the more detailed description hereinafter set forth and be realized in the practice of the invention with the advantageous characteristics resulting from this invention. An additional feature is the depth appearance or stereoscopic ef feet, a mor brilliant and truer effect of colored rays projected on the screen, which assures greatly improved visibility of demonstrating color photography and color moving pictures. To mention only one of the practical effects, the pictures in a theatre or hall become much clearer when viewed from seats at the sides, and the visibility is more uniform from a larger range of distances in the front and to the sides of the centre of the screen, than in the case of jscreens heretofore used. Conversely, just as good visibility practically throughout the different positions of an audience can be assured with this improved screen, as Is now the case in the centre line of the theatre, but

with lesser intensity of projecting light.

The accompanying drawing represents a fragmentary sectional view of a portion of a screen in which F is a fabric or other suit-. able screen backing, B is a binder dried on to the fabric surface, and S represents opaque crystals held by the binder mainly on the side juxtaposed to the fabric, and with opaque facets substantially clear of binder facing outwardly to form the operative surface.

A particular embodiment of my invention involves the coatin of the fabric or other suitable screen bac ring or screen proper, with particular forms of a crystalline substance such as calcium tungstate which is readily provided in a very fine crystalline and white. Such calcium tungstate has the property which enables me to produce the results, and I can readily and economically produce such crystals in any desired quantity for the purpose, and of a size that will pass through 200 mesh. I then mix them with an approximately three per cent solution of gelatine and water having approximately 50 per cent by weight of glycerine mixed with the gelatine, which is added to keep the gelatine soft. Such a mixture can be readily painted on the surface of the screen proper either with a brush or it can be sprayed so that adhesion of the crystals onto the surface is perfect, and on drying,

.the small amount of gelatine is mainly between the crystal surfaces facing the screen proper but on the other hand any small proportion of the gelatine that may cover the visible sides of the crystals does not interfere with light-projecting properly to any serious extent.

For the production of such screens I precipitate the calcium tungstate from a water solution of tungstic acid or sodium tungstate with the addition of calcium chloride, producing in very fin crystalline state the material which is then mixed with a small amount of gelatine and water, and with glycerine to about half of the gelatine content, Which provides a simple, economical and practical mixture to apply to the sur-' face uniformly and in a way that assures adhesion for all of the service and manipulation to which such a'screen is ordinarily subjected.

While such an example of an embodiment of my invention has given most excellent results in test demonstrations I have made, it involves essentially the coating of the screen having innumerable small crystals with bright, reflecting flat surface, the crystals themselves being opaque and white, and as a result a larger amount of light is reflected and the image so reflected is given greater depth and in many cases appears almost stereoscopic. Owing to the reflection of part of the rays by the flat surface of the crystals acting as minute mirrors, there is a greatly improved visibility of all projections, and particularly colors thrown on the screen likewise become more brilliant. I find that such a screen will reflect from ten to fifteen per cent-more light than magnesium carbonate, which has heretofore been regarded as the best screen coating and as reflecting most light of an substance known or heretofore used for sue purposes.

The advantageous results obtained by this invention involve the reflection of light, but not any transformation such as the production of fluorescence, in the material.

In the production of the material, crystals can be readily provided that will pass through 200 mesh but even crystals of the desired characteristics which will pass through 100 mesh are effective, though the use of such larger crystals Will'under certain conditions of projection and observation result in bright spots or slight scintillation which can be entirely avoided for any particular conditions for which these screens are desired, by avoiding the use of crystals of too large a size. As it may be desired to use such surfacing on articles or devices where very close observation is involved, still finer crystals may be used. However, in the service for screens for moving pictures for which this invention will be of the great est commercial value and use, the most striking advantages are obtained with perfectly practical results with 200 mesh crystals, of calcium tungstate.

It will be understood that in the practice of this invention various crystals of various kinds may be used and the surfacing provided, With distinct and substantial ad vantages, may be appliedin various ways and may be applied not alone to screens for moving pictures but for a great'variety of purposes where better visibilit or observation of reflected light is desire or is an improvement in many practical ways for any of the particular purposes to which this improvement may be applied.

' In particular the production of such screens is relatively more economical than many greatly inferior screen surfacings heretofore used, it can be readily applied,.it is a durable surfacing and in general meets all of the practical conditions of commercial use. i

The application may be made to fabrics or any kind of material desired to form the base or background for screens, or may be appllied on a wooden or metal backing or wa Without limiting myself to the particular illustration of one embodiment above described, what I claim as my invention and desire to secure by Letters Patent is:

1. A screen for picture projecting having a coating of small crystals of calcium tungstate and an adhesive securing said crystals to form a contiguous surface.

2. A screen coating consisting of crystals of calcium tungstate and'a binder, a fabric or like backing to which said binder is held by drying after application of the mixture of the binder and the calcium tungstate.

3. A moving picture screen comprising a 7 backing or body, a gelatinous adhesive and calcium tungstate covering the surface of said adhesive to form the visible surface of the screen. j

4;. A picture projecting screen having its surface painted or sprayed with a mixture of fine crystals of calcium tungstatewith an approximately 3 per cent solution of gelatine and water and approximately one-half as much as the gelatine addition by weight of glycerine or like softening material.

In testimony whereof, I have signed my name to this specification this 10th day of March, 1925.

EDWARD R. HEWITT, 

